This invention relates to the polymerization of fluoropolymers into substrates comprising wood and wood by-products substrates. The fluoropolymer/substrate network that results is present on the surface of the substrate and is also deposited into the substrate at appreciable depths. The substrate/fluoropolymer networks provide a protective coating for the substrate.
Wood, like other porous materials has a host of uses. Common uses for wood include use as a building material and for the production of furniture. Materials comprising wood may degrade by staining and wetting. Materials comprising wood degrade by staining, wetting and warping. It is desirable to treat porous wood substrates such that they are more resistant to degradation. It is also desirable to treat wood such that the wood is more resistant to decay and degradation by staining, wetting and warping, and to improve durability while maintaining the appearance of wood.
For many years, textiles have been chemically treated to improve water and oil repellency. Different applications are commercially available to protect different kinds of substrates from oil and water staining. For example, Scotchgard(copyright), sold by the 3M Company, and Zonyl(copyright), sold by E. I. du Pont de Nemours and Company, are available to consumers for use with textiles and fabrics. However, these methods have not been applied to wood substrates.
There are several references which have used fluoro-compounds in wood to enhance the properties of wood. For example, U.S. Pat. No. 3,962,171 discusses a protective coating composition. The composition is used for painted and unpainted metal, plastic and wood surfaces. The method comprises preparing a mixture of a solution of 20 parts of granular polytetrafluoroethylene in Freon(copyright). The composition is sprayed onto an acrylic painted surface, dried and wiped to form a transparent coating.
The use of granular fluoro-compounds is also discussed in Japanese Patent 05318413. The invention involves a method whereby a raw wood material is impregnated with a fluorinated microparticles having a diameter of 5 microns and a compound which changes to insoluble cured resin. The compound is cured to fix the microparticles with the resin. The uses and advantages listed in the abstract include use as building materials, woody appearance, contamination resistance, moisture and water resistance. The invention does not teach polymerization of a fluoro-compound into the wood as the present invention does.
Other references include the treatment of microporous materials with fluoroacrylate to achieve permanent water and oil repellency. For example, U.S. Pat. No. 5,156,780 teaches a method for treating microporous substrates to achieve water and oil repellency while maintaining porosity. In the ""780 method, the substrates are impregnated with a solution of monomer in a carrier solvent. The carrier solvent is first substantially removed from the substrate for the express purpose of leaving the monomer as a thin conformal coating on all internal and external substrate surfaces. In this manner, the monomer is converted to polymer and the polymer does not block the pores or restrict flow in subsequent use as a filtration membrane.
It is desirable to treat the wood such that the wood is more resistant to staining, warping and wetting. It is also desirable to treat other porous substrates such that the other substrates are more resistant to degradation by staining and wetting.
The present invention teaches a fluoropolymer/substrate composition wherein the presence of fluoropolymer functions as a protective material for the substrate. The method used leaves the initiator and the initiator carrier solvent in the substrate during polymerization and uses undiluted monomer or, in its preferred embodiment, gaseous monomer, with the intention of penetrating and blocking all pores to the greatest depth possible. The object of the present invention is to provide a method for treating the substrate such that the presence of the fluoropolymer/substrate composition decreases or eliminates penetration of agents causing degradation so as to increase the substrate""s resistance to wetting by oil and water, reduce staining by oil, water, and common materials such as ketchup, and to improve durability. The fluoropolymer/wood networks of the present invention have decreased water absorption and have improved resistance to degradation, staining, wetting, and warping and may be used for building materials. The fluoropolymer/non-wood substrate networks of the present invention have improved resistance to staining and wetting.
Disclosed in the present invention is a process for preparing a fluoropolymer/substrate composition, comprising:
in the case of gaseous fluoromonomer
(a) contacting a porous substrate with a solution comprising an initiator dissolved in a suitable solvent;
(b) exposing said substrate and said initiator to gaseous fluoromonomer, under polymerization temperature and pressure conditions, wherein the fluoromonomer polymerizes into said substrate;
or in the case of liquid fluoromonomer
(a) preparing a solution comprising initiator and liquid fluoromonomer;
(b) contacting a porous substrate with said solution; and
(c) polymerizing the liquid fluoromonomer under polymerization temperature and pressure conditions, wherein the fluoromonomer polymerizes into said substrate, optionally in the presence of gaseous fluoromonomer, into said substrate.
The present invention also provides for a composition of matter made by a process for preparing a fluoropolymer/substrate composition, comprising:
in the case of gaseous fluoromonomer
(a) contacting a porous substrate with a solution comprising an initiator dissolved in a suitable solvent;
(b) exposing said substrate and said initiator to gaseous fluoromonomer, under polymerization temperature and pressure conditions, wherein the fluoromonomer polymerizes into said substrate;
or in the case of liquid fluoromonomer
(a) preparing a solution comprising initiator and liquid fluoromonomer;
(b) contacting a porous substrate with said solution; and
(c) polymerizing the liquid fluoromonomer under polymerization temperature and pressure conditions, wherein the fluoromonomer polymerizes into said substrate, optionally in the presence of gaseous fluoromonomer, into said substrate.
Another disclosure of this invention is a composition of matter, comprising: a substrate which further comprises polymerized fluoropolymer, wherein the substrate is an open pore structure with interconnecting pores throughout said substrate, and wherein the level of fluoropolymer within and on the surface of said composition is from about 0.1 percent to about 300 percent of the weight of said substrate.